I recently received and tested the first 1.8V Ethernet FMCs and they are now available to buy on ethernetfmc.com. There are two main reasons why you’d actually want a 1.8V version: Firstly, some carriers only support VADJ of 1.8V (such as the VC707 and VC709). Secondly, some customers need to match it with another 1.8V FMC on a dual-FMC carrier.
Releasing the new version didn’t come without headaches. Most FMC carriers on the market have a 2.5V VADJ by default, so there’s a good chance of frying the Ethernet PHYs on first go. Luckily I haven’t made that mistake yet! The other “problem” is the fact that the board provides a 125MHz LVDS clock – respecting the Vita 57 standard – but creating a problem for carriers with FMCs that route to HR (high-range) banks. Which is most of them! Yes the ZedBoard, AC701, KC705, ZC702 and ZC706 all route to HR banks. HR banks require you to define your LVDS I/Os with the
LVDS_25 IO standard (ie. the 2.5V standard), but we’d really want to be using the
LVDS (1.8V) IO standard. So I had to either declare non-compatibility or find a workaround. Fortunately, there is a workaround and I’ve written about it here:
So if you need an Ethernet FMC that works at 1.8V, now you can have it!